Community engaged tick surveillance and tickMAP as a public health tool to track the emergence of ticks and tick-borne diseases in New York

Diversity of Ticks and Rickettsiae in the Southwestern United States: Implications for Public Health

Background: Surveillance is important in addressing the significant public health concerns posed by tick-borne diseases. However, the southwestern U.S. presents particular challenges due to diverse tick fauna and varied ecologies. Methods: From 2021 to 2022, we conducted a partner-based tick surveillance program in Arizona and California to assess the presence of Rickettsia spp. pathogens and species composition of tick vectors. Results: A total of 913 ticks was collected, comprising in descending abundance Rhipicephalus sanguineus, Dermacentor similis, Ixodes pacificus (I. pacificus), Argas sp., Otobius megnini, and Haemaphysalis leporispalustris. Arizona submitted predominantly brown dog ticks (90.05% of all ticks from Arizona), while California showed greater tick species richness with five species identified. No Rickettsia rickettsii was detected, but a variety of other Rickettsia spp. was found in ticks from both Arizona and California and included Rickettsia rhipicephali (R. rhipicephali), Rickettsia massiliae, and Rickettsia monacensis-like rickettsial agents of I. pacificus, and two rickettsial organisms that were not identified to species: one Rickettsia montanensis or Rickettsia raoultii-like, and the other most similar to Candidatus Rickettsia tarasevichiae (R. tarasevichiae). Conclusion: This research contributes to our understanding of tickborne diseases in the southwestern U.S., and emphasizes the need for targeted surveillance and intervention initiatives in a region with complex relationships among ticks, hosts, and Rickettsia species. In particular, the finding of an apparently novel pairing of an unknown Argas sp. tick and R. tarasevichiae-like organism suggests that argasid species are an important target for future research. In addition, the results-both tick species submitted and resulting Rickettsia spp. identified-highlights the strengths and potential biases associated with a partner-based sampling method for tick surveillance.

Early transcriptomic changes at the skin interface during Powassan virus transmission by Ixodes scapularis ticks

Introduction

Powassan virus (POWV), a vector-borne pathogen transmitted by Ixodes ticks in North America, is the causative agent of Powassan encephalitis. As obligate hematophagous organisms, ticks transmit pathogens like POWV at the tick bite site, specifically during the initial stages of feeding. Tick feeding and salivary factors modulate the host's immunological responses, facilitating blood feeding and pathogen transmission. However, the mechanisms of immunomodulation during POWV transmission remain inadequately understood. In this study, we investigated the global cutaneous transcriptomic changes associated with tick bites during POWV transmission.

Methods

We collected skin biopsies from the tick attachment sites at 1, 3, and 6 h after feeding by POWV-infected and uninfected ticks, followed by RNA sequencing of these samples. Differentially expressed genes were analyzed for pathway enrichment using gene ontology and pathway enrichment analyses.

Results

Our findings reveal that tick feeding alone significantly impacts the skin transcriptome within the first 1 to 3 h of tick attachment. Although early POWV transmission induces minimal changes in the local environment, a pronounced shift toward a proinflammatory state is observed 6 h after tick attachment, characterized by neutrophil recruitment and interleukin signaling.

Discussion

These transcriptomic data elucidate the dynamic changes at the tick bite site, transitioning from changes that assist blood meal acquisition to a proinflammatory phase that may facilitate viral dissemination.

Neurological Complications Associated With the Powassan Virus and Treatment Interventions

Powassan virus (POWV), a flavivirus transmitted by Ixodes ticks, poses significant neurological risks, including encephalitis and meningitis. Despite its growing geographical spread and severe clinical manifestations, no specific antiviral treatments are currently available. This review synthesizes the existing literature on POWV, focusing on its epidemiology, clinical manifestations, neurological impact, and current treatment approaches. The review also explores the molecular biology of POWV, highlighting its genomic structure and the role of nonstructural proteins in its pathogenesis. POWV infection can range from asymptomatic to severe neurological disorders such as encephalitis and meningitis, with the latter presenting less severe outcomes. The pathophysiology of the virus involves immune evasion and robust neuroinflammation, complicating treatment strategies. Current management is supportive, with efforts ongoing to repurpose existing antivirals and develop new therapeutic interventions. Prognostic disparities between POWV-induced meningitis and encephalitis are notable, with meningitis generally having more favorable outcomes. The review also identifies critical gaps in POWV research, particularly in understanding the long-term neurological impacts and developing specific antiviral therapies. This article collates existing relevant literature on the POWV and culminates in two strategic actions: firstly, in the absence of an existing vaccine, it proposes repurposing antiviral drugs designed for related flaviviruses to target shared molecular pathways, such as nonstructural proteins in the POWV. Secondly, the article advocates for longitudinal studies to explore the long-term neurological effects on individuals who have survived POWV infections.

Risky business: human-related data is lacking from Lyme disease risk models

Used as a communicative tool for risk management, risk maps provide a service to the public, conveying information that can raise risk awareness and encourage mitigation. Several studies have utilized risk maps to determine risks associated with the distribution of Borrelia burgdorferi, the causal agent of Lyme disease in North America and Europe, as this zoonotic disease can lead to severe symptoms. This literature review focused on the use of risk maps to model distributions of B. burgdorferi and its vector, the blacklegged tick (Ixodes scapularis), in North America to compare variables used to predict these spatial models. Data were compiled from the existing literature to determine which ecological, environmental, and anthropic (i.e., human focused) variables past research has considered influential to the risk level for Lyme disease. The frequency of these variables was examined and analyzed via a non-metric multidimensional scaling analysis to compare different map elements that may categorize the risk models performed. Environmental variables were found to be the most frequently used in risk spatial models, particularly temperature. It was found that there was a significantly dissimilar distribution of variables used within map elements across studies: Map Type, Map Distributions, and Map Scale. Within these map elements, few anthropic variables were considered, particularly in studies that modeled future risk, despite the objective of these models directly or indirectly focusing on public health intervention. Without including human-related factors considering these variables within risk map models, it is difficult to determine how reliable these risk maps truly are. Future researchers may be persuaded to improve disease risk models by taking this into consideration.

Serologic Testing for Rocky Mountain Spotted Fever in a Low-Incidence Region

BACKGROUND

Tick-borne diseases have grown in incidence over recent decades. As a result, diagnostic testing has become more common, often performed as broad antibody-based panels for multiple tick-transmitted pathogens. Rocky Mountain spotted fever (RMSF) is rare in our region yet may cause severe morbidity, leading to diagnostic screening in low-risk patients. We sought to describe trends in RMSF diagnostic testing, rate of IgG seropositivity, and clinical features of those tested.

METHODS

We performed a retrospective chart review of patients ≤21 years old undergoing testing for RMSF and/or with an ICD-9/10 code for RMSF. Patients were categorized by infection likelihood based on clinical and laboratory criteria adapted from Centers for Disease Control and Prevention's (CDC) case definition of spotted fever rickettsioses. Clinical data were collected and analyzed with descriptive statistics.

RESULTS

One hundred and seventy patients were included. 5.8% met CDC criteria for rickettsial infection, 6.5% had an elevated IgG titer but lacked suggestive symptoms, and 87.6% had a negative IgG titer. Many patients tested were unlikely to have RMSF, including 50% lacking fever, 20% lacking any RMSF "classic triad" symptoms, 13% without acute illness, and 22% tested during months with low tick activity. Convalescent serology was performed in 7.6% of patients and none underwent Rickettsia rickettsii polymerase chain reaction (PCR) testing.

CONCLUSIONS

Diagnostic testing was frequently performed in patients unlikely to have RMSF. We identified many opportunities for improving test utilization. Reserving testing for those with higher pretest probability, performing convalescent serology, and utilizing PCR may improve the accuracy of RMSF diagnosis and reduce clinical challenges stemming from inappropriate testing.

The Lone Star tick, Amblyomma americanum, salivary factors exacerbate the clinical outcome of Heartland virus disease in a small animal model

Heartland virus was first isolated in 2009 from two patients in Missouri and is transmitted by the Lone Star tick, Amblyomma americanum. To understand disease transmission and pathogenesis, it is necessary to develop an animal model which utilizes the natural route of transmission and manifests in a manner similar to documented human cases. Herein we describe our investigations on identifying A129 mice as the most appropriate small animal model for HRTV pathogenesis that mimics human clinical outcomes. We further investigated the impact of tick saliva in enhancing pathogen transmission and clinical outcomes. Our investigations revealed an increase in viral load in the groups of mice that received both virus and tick salivary gland extract (SGE). Spleens of all infected mice showed extramedullary hematopoiesis (EH), depleted white pulp, and absence of germinal centers. This observation mimics the splenomegaly observed in natural human cases. In the group that received both HRTV and tick SGE, the clinical outcome of HRTV infection was exacerbated compared to HRTV only infection. EH scores and the presence of viral antigens in spleen were higher in mice that received both HRTV and tick SGE. In conclusion, we have developed a small animal model that mimics natural human infection and also demonstrated the impact of tick salivary factors in exacerbating the HRTV infection.

Evaluating spatial and temporal patterns of tick exposure in the United States using community science data submitted through a smartphone application

Research initiatives that engage the public (i.e., community science or citizen science) increasingly provide insights into tick exposures in the United States. However, these data have important caveats, particularly with respect to reported travel history and tick identification. Here, we assessed whether a smartphone application, The Tick App, provides reliable and novel insights into tick exposures across three domains - travel history, broad spatial and temporal patterns of species-specific encounters, and tick identification. During 2019-2021, we received 11,424 tick encounter submissions from across the United States, with nearly all generated in the Midwest and Northeast regions. Encounters were predominantly with human hosts (71%); although one-fourth of ticks were found on animals. Half of the encounters (51%) consisted of self-reported peri‑domestic exposures, while 37% consisted of self-reported recreational exposures. Using phone-based location services, we detected differences in travel history outside of the users' county of residence along an urbanicity gradient. Approximately 75% of users from large metropolitan and rural counties had travel out-of-county in the four days prior to tick detection, whereas an estimated 50-60% of users from smaller metropolitan areas did. Furthermore, we generated tick encounter maps for Dermacentor variabilis and Ixodes scapularis that partially accounted for travel history and overall mirrored previously published species distributions. Finally, we evaluated whether a streamlined three-question sequence (on tick size, feeding status, and color) would inform a simple algorithm to optimize image-based tick identification. Visual aides of tick coloration and size engaged and guided users towards species and life stage classification moderately well, with 56% of one-time submitters correctly selecting photos of D. variabilis adults and 76% of frequent-submitters correctly selecting photos of D. variabilis adults. Together, these results indicate the importance of bolstering the use of smartphone applications to engage community scientists and complement other active and passive tick surveillance systems.

The Lone Star Tick, Amblyomma americanum, salivary factors exacerbate the clinical outcome of Heartland virus disease in a small animal model

Heartland virus was first isolated in 2009 from two patients in Missouri and is transmitted by the lone star tick, Amblyomma americanum. To understand disease transmission and pathogenesis, it is necessary to develop an animal model that utilizes the natural transmission route and manifests in a manner similar to documented human cases. Herein we describe our investigations on identifying A129 mice as the most appropriate small animal model for HRTV pathogenesis that mimics human clinical outcomes. We further investigated the impact of tick saliva in enhancing pathogen transmission and clinical outcomes. Our investigations revealed an increase in viral load in the groups of mice that received both virus and tick salivary gland extract (SGE). Spleens of all infected mice showed extramedullary hematopoiesis (EH), depleted white pulp, and absence of germinal centers. This observation mimics the splenomegaly observed in natural human cases. In the group that received both HRTV and tick SGE, the clinical outcome of HRTV infection was exacerbated compared to HRTV-only infection. EH scores and viral antigens in the spleen were higher in mice that received both HRTV and tick SGE. In conclusion, we have developed a small animal model that mimics natural human infection and also demonstrated the impact to tick salivary factors in exacerbating the HRTV infection.

Powassan Virus Lineage I in Field-Collected Dermacentor variabilis Ticks, New York, USA

Powassan virus is a tickborne flavivirus that can cause lethal or debilitating neurologic illness. It is canonically transmitted by Ixodes spp. ticks but might spill over to sympatric Dermacentor species. We detected Powassan virus lineage I from a pool of field-collected D. variabilis ticks in New York, USA.

Human attachment site preferences of ticks parasitizing in New York

Ticks transmit several arthropod-borne pathogens in New York State. The primary human-biting ticks in this region are Ixodes scapularis, Amblyomma americanum, and Dermacentor variabilis. Body regions where tick bites human vary depending on the tick species and life stage, and clothing worn by the host. A community tick submission system was used to acquire information about bite-site location prior to pathogen testing to understand species and life stage-specific body-segment preferences. These data resulted in the identification of species-specific preferences for location, with D. variabilis preferentially biting the head and neck and A. americanum preferring the thighs, groin, and abdomen. Ixodes scapularis was found across the body, although it showed a significant life stage difference with adults preferring the head, midsection, and groin, while nymphs/larvae preferred the extremities. Infection with Borrelia burgdorferi resulted in a significant change in attachment site. This provides an assessment of which body region ticks of the most common species in New York are likely to be found.

Tick species infesting humans in the United States

The data for human tick encounters in the United States (US) presented in this paper were compiled with the goals of: (i) presenting quantitative data across the full range of native or recently established human biting ixodid (hard) and argasid (soft) tick species with regards to their frequency of infesting humans, based on published records of ticks collected while biting humans or crawling on clothing or skin; and (ii) providing a guide to publications on human tick encounters. Summary data are presented in table format, and the detailed data these summaries were based on are included in a set of Supplementary Tables. To date, totals of 36 ixodid species (234,722 specimens) and 13 argasid species (230 specimens) have been recorded in the published literature to infest humans in the US. Nationally, the top five ixodid species recorded from humans were the blacklegged tick, Ixodes scapularis (n=158,008 specimens); the lone star tick, Amblyomma americanum (n=36,004); the American dog tick, Dermacentor variabilis (n=26,624); the western blacklegged tick, Ixodes pacificus (n=4,158); and the Rocky Mountain wood tick, Dermacentor andersoni (n=3,518). Additional species with more than 250 ticks recorded from humans included Ixodes cookei (n=2,494); the Pacific Coast tick, Dermacentor occidentalis (n=809); the brown dog tick, Rhipicephalus sanguineus sensu lato (n=714); the winter tick, Dermacentor albipictus (n=465); and the Gulf Coast tick, Amblyomma maculatum (n=335). The spinose ear tick, Otobius megnini (n=69), and the pajaroello tick, Ornithodoros coriaceus (n=55) were the argasid species most commonly recorded from humans. Additional information presented for each of the 49 tick species include a breakdown of life stages recorded from humans, broad geographical distribution in the US, host preference, and associated human pathogens or medical conditions. The paper also provides a history of publications on human tick encounters in the US, with tables outlining publications containing quantitative data on human tick encounters as well as other notable publications on human-tick interactions. Data limitations are discussed. Researchers and public health professionals in possession of unpublished human tick encounter data are strongly encouraged to publish this information in peer-reviewed scientific journals. In future papers, it would be beneficial if data consistently were broken down by tick species and life stage as well as host species and ticks found biting versus crawling on clothing or skin.